The Cold Equations
by stana1701
Summary: It's winter in New York and the city is in the grip of a killer cold-snap


The Cold Equations

"Kate, I can't feel my toes, and I'm pretty sure my nose has frostbite. How much longer are you going to be?" Rick Castle hunched his shoulders and dug his hands deeper into his pockets, trying to squeeze some warmth into his frozen body. It was four-thirty in the morning and they'd been at this murder scene for over an hour. The temperature was well below zero as a record cold-spell gripped New York.

"I told you to stay in bed," Detective Kate Beckett replied. She was walking carefully around a yellow cab parked on a dark, lonely street. The body of a young cab driver lay slumped over the steering wheel, his eyes open and unseeing. "You could have met me at the precinct later. You can help out on a case without coming to the crime scene at three in the morning you know." Beckett didn't even look cold as she moved around the scene taking notes, while Castle could feel the last remnants of his body heat escaping out through the bottom of his frozen feet. He felt about as warm as the body in the cab. Much longer out here, he'd be about as alive too.

He hopped from one foot to the other trying to stay warm. He never missed a crime scene, no matter what time or what temperature, and he wasn't going to start now. Helping Kate solve crimes had become more important to Castle than writing about them, and now that they were together, he felt even more protective of her than he had before. Though he would never admit it to her, one reason he wanted to be around when she went to check out a new crime scene was to make sure she was safe. He found that if he stayed at home in bed while she was out on a late night call, all he did was lie awake and worry about her, so he might as well just get up and go with her. Still, this sub-zero weather was making him question whether a warm bed and being worried wouldn't have been a better choice this one time.

Attempting to get his mind off his frozen toes, Castle moved in to take another look at a crime scene he'd already been over. The victim was a young cab driver who had been shot in the back of the head with a small caliber handgun, probably a twenty-two. A gun that small usually wasn't deadly, but when fired into the head, it penetrated the skull only once and then, not having enough power to exit out the other side, it bounced around inside the skull, scrambling the victim's brain and killing them. Larger caliber gunshots to the head often just left a hole going in and going out. It was astonishing how many people survived a larger-caliber gunshot to the head.

Only a dark patch of blood in the back of the cabbie's head indicated the mortal wound. It was so cold, the blood had frozen and you could see the little ice crystals around the dark stain. So cold, in fact the cabbie's entire body was frozen, and when the Medical Examiner - someone Castle didn't know - was finally done, the police had trouble getting the body out of the cab. It maintained the posture of bent knees and arms, and when they finally wrestled it onto the gurney, the arms and legs stuck up in what would have been a comical sight if not so gruesome.

"Ok, that's enough, we can head back now," Beckett finally said and Castle was in the car before she'd finished saying it. "Want me to drop you off at home?" she asked.

"Aren't you coming home too?"

"No, I'm going in. This is the third murder of a cab driver in the last year, so there's going to be a lot of pressure on the mayor to get something done, which puts pressure on Gates, which puts pressure on me. Gates will want to know as much as possible by the time she gets in, so I better be prepared. Why don't I take you home so you can take a hot shower? Just bring me some coffee and something to eat later."

"Hard to argue with that," Castle replied and together they left the crime scene and the freezing cold behind.

After a very long and very hot shower, Castle finally set out for the precinct at the far more civilized hour of 8am. He put on his thickest, warmest coat and wrapped a scarf securely around his neck and then braced himself to meet the cold. He winced as the sub-zero air hit him in the face. He pulled the collar of his jacket up around his neck and pushed his hands deep into pockets and headed down the street to the subway station. He'd thought of calling a cab to take him to the precinct, but remembered Kate's admonishment at how elitist it looked when he got out of a cab in front of the police building. Just trying to be another one of the gang at the precinct had its disadvantages. He endured the cold, endured the subway packed full of bundled up, grumpy New Yorkers, and wondered how much more he was willing to endure to make Kate happy. A lot more, he quickly realized, and shrugged aside the discomfort of the cold as it hit him again coming out of the subway.

After walking a half block, he saw one of the regular homeless folk that lived in an alley near the precinct frantically waving at him. It was Wanda, a dread-locked, middle-aged black woman who talked to herself and to anybody else passing by. As Castle came up to her, she started talking quickly, obviously agitated. "Marty didn't come home last night," she said, close to hysteria. "Marty is gone and someone got to find him." She gave Castle a pleading look. "Please, please, please, someone got to do something" she implored. She knew Castle to be a kind, generous person from the many times he had stopped to give her money and how he would occasionally chat with her, learning her name and a bit about her, like how she had once sold hot dogs at a stand outside the World Trade Center. Wanda's friend Marty was another fixture here on this corner, a 30ish white guy who also talked to himself and was often agitated for seemingly no reason, but other than that, a nice enough guy.

"It's really cold Wanda, could he have slept in a shelter last night?" Castle asked.

Wanda shook her head vigorously. "No no no no, never. We never sleep in shelters, they too dangerous. There's a steam vent here, keeps us warm at night. We have our little place here, nice and safe near the police station."

Castle could see the cloud of steam in the alley amidst the trash bins and other garbage. It looked like someone had rigged up a makeshift shelter between the bins using pieces of cardboard. He supposed it would be survivable in that little hovel if one had enough clothes and a thick sleeping bag and stayed close to the steam vent. God he was glad not to be homeless. He looked into Wanda's pleading eyes. "Ok, ok, I'll see what I can do" he told her.

His words weren't enough for Wanda though. "You have to promise," she said, getting in close and looking up into his eyes. "No one cares about us, no one cares when we disappear. But Marty, he's someone, he matters, he matters to me!"

That got to Castle, the thought of how most people just ignored the homeless, unconcerned about their lives and their hardships. He reached out and touched Wanda's arm. "Okay, I promise, I will look into it," he told her. "I will see what I can do to find Marty."

Wanda smiled and gave Castle a hug, overwhelming him with the strong smell of her unwashed body. He wanted to push her away, but instead he hugged her back. After, she looked up at him. "Thank you thank you, I knew you would care, you always care." There were tears in her eyes and Castle was suddenly shamefully embarrassed.

"As soon as I find out something I'll let you know," he told her and then hurried to get inside the precinct building.

"You promised _who_ _what_!" Beckett exclaimed after he explained it all to her.

"Wanda, you know, that homeless lady from the alley. She said Marty was missing and asked me to look into it. She probably thinks I'm a cop or something," Castle explained rather sheepishly.

"So you told her yes? Even though you don't know anything about her or this Marty person? Castle, do you realize how hard it is to track down transients? How much time and effort it takes?" She stood by the whiteboard she was setting up for the cabbie murder, hands on hips, shaking her head at him in irritation. She wasn't exactly mad at him, but she wasn't pleased either. She was a homicide detective, a very busy one, and the last thing she needed was Castle taking up some of her time asking her for help tracking down a missing transient. It was touching how he cared about everyone, but his generosity could be damn annoying too, especially when it invariably led to her involvement.

"I know, I understand how hard it is, how busy you are" Castle replied. "I'll do it on my own, I won't bug you at all, I promise."

"Ok fine, then where are you going to start? What's your plan?" she asked.

"Well, um, I'm not sure… check out the shelters around here maybe?" He cringed, knowing he already could use a bit of her help.

Kate sighed. "If it were me, I'd start with the morgue. It's harsh, I know, but when it's this cold, and a transient goes missing, that's the first place I would check, the city morgue." Castle nodded and Kate continued. "So does this mean you won't be riding along on this new case we picked up last night?"

Castle frowned. "Yeah I guess I'll have to sit this one out until I solve my own case. Think you can manage without me?"

"It will be tough, but I'll get by" she replied sarcastically. "Though seriously, I could really use your help. Ryan and Esposito have another case to work on, while the mayor is breathing down Gates neck on my case. New York depends on those cab drivers and it doesn't look good if they keep turning up dead."

Kate turned to the white board. A picture of the dead cabbie was all she had for now. Castle watched her for a moment, wishing he could work the case with her, but then turned to the phone and got busy, calling the county morgue, as Kate had recommended. The morgue receptionist told him two John Does had been picked up last night frozen to death, and yes, he could come in and have a look. Castle got up to go, giving Kate a quick smile on his way out. "I'll see you soon" he said, "I'm headed to the morgue." Kate nodded her head and dismissed him with a wave of her hand.

Another trip out into the cold, but this time, elitism be damned, Castle called a cab to take him over to the morgue. He was there in 10 minutes and soon found himself in the dreary confines of New York's morgue. A young, perky female attendant dressed in scrubs and far too happy for such a morose place, greeted him cheerfully and led him downstairs. He found her cheerfulness a bit creepy amidst all this death. She showed him to where the two unidentified bodies were being held. The first body was that of a young Latino male, definitely not Marty. He'd been found over by Central Park. There was a large population of homeless illegal immigrants in New York and freezing weather like this was a challenge that this young man had been unable to cope with.

The second body the attendant showed him was a white male, and Castle knew right away it was Marty. He too had apparently succumbed to the frigid conditions last night, his body showing no obvious signs of trauma. Castle thanked the cheerful attendant and headed back to the precinct for the unwelcome job of notifying Wanda. He took a picture of Marty's corpse to show Wanda so that she would know for certain he was dead.

Wanda was understandably distraught at the news. It took five minutes of her wailing before she finally calmed down enough to ask details of his death. "Where'd they find him? How did he die? What happened, what happened, how could this happen? God oh god help me!" she wailed.

"He was found over by the George Washington Bridge. I'm afraid he froze to death." Castle patted her arm awkwardly in an attempt to comfort her.

Wanda shook her head. "No, no, that's not possible. He would never go there, he always slept here, always, every night. He and me, we alley buddies, we like a married couple. He would never sleep anywhere else. Besides, he knew how to take care of himself; he would never let this happen. Someone must have done something to him, something bad happened, he wouldn't have just gone off like that…" she finally broke off, sobbing. Castle was at a loss how to handle this and really wished Beckett was there. She would know what to say, what to do, how to extricate herself from this delicate situation. The best he could think to do was to ask questions.

"What was Marty's usual routine?"

"He and I always ate dinner at the Mission, then come here to sleep. During the day, we go our separate ways. He always went to a coffee shop over by Colombia University, said he worked there doing his math, that people gave him coffee and food and let him sit around without bothering him. He has these notebooks he writes in all the time, full of math stuff. Only last night, he didn't come for dinner, he didn't show up and now he's dead. My god, what am I gonna do?"

Castle frowned. It did seem odd that Marty would be found frozen to death in some cold little park by the river when every other night he'd slept here by the precinct. Damn it, he thought, it had to be that way, didn't it? It couldn't just be an open and shut case of accidental death. It would bug Castle, and not just because Wanda was so upset. Anybody other than a transient, any regular person living a normal, comfortable life, and their death would be looked into. But Marty was homeless. Did that make his death any less important?

Unfortunately, Castle had a good idea how the NYPD would view this death. He knew what their response would be when he asked them to officially look into it. Someone would go through the motions of pretending to care when really the case would be written off after some cursory investigation.

Castle took Wanda by the shoulders and looked into her eyes. "Wanda, I promise you, a full investigation will be done, okay? I will make sure we find out what happened to Marty." Wanda gave Castle a sad smile through her tears. "Thank you, thank you," she said. And all Castle could think was: Beckett is not going to like what he had in mind….

"What do you mean, you want to look into it yourself?" she asked, exasperated at his persistence with this. "You do know there is procedure to follow here? That all you can do is talk to the investigating officer? That you, not having an official role in NYPD, have no authority to act on this case?"

"I know, I know, I already did contact the investigating officer. And you know what he said?" Here it comes he thought, she's going to love this… "He said, since the victim lived near this precinct, he'd be happy to transfer the case over here, so I told him that would be great." Castle smiled hopefully.

"You did what!" Beckett cried. Castle cringed at her words.

"I had him transfer the case here," he replied meekly. "To you specifically. He was very happy to do it." Another hopeful smile. Castle made sure to stay out of arms reach of Beckett.

Beckett pursed her lips tight together and looked like there was a lot more she wanted to yell at him. But instead, she took a few deep breaths, closed her eyes for a moment, then spoke in a normal, if somewhat irritated voice. "Fine then, but you do all the work. You make the calls, you notify next of kin, you visit the scene. But -and this is important - if you find anyone who looks suspicious, you tell me, right, and we look into it together? No risk taking here, okay?"

"Okay," Castle replied with a relieved smile.

"Promise? Safety first?"

"Promise. Safety first," he repeated.

Beckett shook her head. What am I going to do with him, she thought to herself.

Now that he had dodged the wrath of Kate, Castle was actually excited to have a case all his own. This had never happened before, and he was eager to get started. The first thing he did was call Lanie, the Medical Examiner he and Beckett were close friends with, and through charm, cajoling, and a promise of two courtside Knicks tickets, Castle convinced Lanie to take a thorough look at Marty's body and to also to see if she could expedite the running of his fingerprints.

After the call, more to get out of Beckett's way than anything else, Castle decided to first check out the sight where Marty's body had been found. He didn't relish the idea of walking around outside in the cold, but it beat hanging around the precinct, getting in Beckett's way. Wrapping himself up tightly against the cold, Castle left Beckett with a quick goodbye. She waved quickly at him as he left, too busy to give him any more grief.

Alone now, Kate Beckett leaned against a desk, staring in frustration at her nearly empty murder board. Detectives Ryan and Esposito were off investigating their own case, so she had the office to herself. It wasn't just Castle's going and adding another difficult case to her load that bothered her. It was her current case, the cab driver's death that troubled her the most. He was just a kid, nineteen years old, borrowing his brother's cab to make some extra money. The distraught brother had told her what a nice kid he was, how he loved talking to people about everything, how everyone liked him, how he was too trusting, and how devastated his family was by this loss.

What really bothered Kate about this case was the likelihood it would never be solved. It was a random crime committed by an assailant that had no connection to the victim and she had no physical evidence available to help solve the case. The only piece of evidence she did have was the twenty-two-caliber bullet taken from the cabbie's brain. She didn't even have any information yet on the route the cabbie had taken that fateful night because the kid had turned off the cab's tracking device. His use of the cab was off the books; he wasn't actually licensed to drive his brother's cab, so he'd turned off anything recording his use of it. Beckett had a call to the guys down in the tech department to get her GPS data on the cab, but they'd told her it would take a few days because of the backlog. Every request around here had a backlog; NYPD existed on a backlog because it was operating on a shoestring budget. Everyone wanted crimes solved and people protected, but no one wanted to pay for it. Beckett knew she had a long and frustrating day ahead of her.

Castle had better luck with evidence than Beckett. When he returned from checking out the sight where Marty's body had been found, there was a message from Lanie waiting for him. True to form, the ME had not disappointed. They had an ID on Marty from his fingerprints and she'd completed her exam of the body. His full name was Martin Sawyer and the last official record of him was as a student at CUNY eight years ago. More important was that she had finished her exam and had found a suspicious needle mark on the back of his neck, right under the hairline. She'd run a tox screen on his blood and found traces of Ketamine in his system. Castle was familiar with Ketamine and its ability to knock out its victims back from when he and Beckett had been knocked out with the drug and woke up in a strange building, handcuffed together. He smiled at the memory. That was back when they were still dancing around their feelings for one another.

Castle felt oddly elated at Lanie's news. A suspicious needle mark…it sounded like this really was a murder. It was a murder and it was his case, his very own case, Beckett had made that clear. Wow, he felt like a real detective. But then Castle remembered the victim. Sorry about that Marty, he thought to himself. But it is kinda cool.

Using Beckett's computer, Castle was also able to find Marty's only living relative, a brother with an address listed across the river in New Jersey. This was a part of the investigation Castle had not thought about, and did want to do, notifying the family. But Beckett had made it clear to him that he had to do take care of all the legwork, so Castle called Marty's brother, Jimmy Sawyer, on the phone.

"Marty's dead? When, how did it happen?" Jimmy asked. He was six years younger than Marty and sounded genuinely broken up by the news, which surprised Castle, given Marty's homeless history.

"He died last night. He was found in a park in Manhattan, frozen to death. We're investigating his death now," Castle replied, trying to sound both sympathetic and official but feeling he had fallen way short of Beckett's standards.

"I can't believe this. Our dad died just last week. I've been looking for Marty to tell him, to tell him and to get him some help. Dad didn't have a will, so everything gets split between Marty and me. There was quite a bit of money, and the house. I thought Marty and I could move back home…" There was a pause as Jimmy took this all in. "He's my only family… I really wanted to help him…" his voice drifted off.

"I'm really sorry about all this," said Castle trying to sound sympathetic, when actually the wheels of suspicion were starting to turn in his head. "I see you live in Hoboken. We're going to need you to come over and identify the body and answer a few questions."

Jimmy Sawyer was sitting in the interview room by the afternoon, after he'd been to the morgue to positively ID the body. Beckett joined Castle for the interrogation.

"So Jimmy, you were looking for your brother, but never found him?" Beckett asked, flipping through the meager case notes casually.

"That's right. I haven't seen him for almost ten years, ever since Dad kicked him out of the house. No one saw him after that."

"Why did your dad kick him out?" asked Castle.

"Because he was starting to go crazy. He talked to himself all the time, and he stopped taking care of himself. Dad took him to a doctor, who diagnosed him as a Schizophrenic, but Marty wouldn't take the medicine the doctor prescribed. He told me it made him stupid."

"Were you and he close?" asked Beckett.

"Not exactly close. He was weird, but we got along ok. My mom had died a while ago and it was just my dad, Marty, and I, so Marty, being older, tried to help out taking care of me. But it was more like I took care of him. Maybe he was schizo, but he was also different because he was so smart, and that made him special. My dad and I would get into arguments about what to do with Marty. Dad couldn't stand the way Marty acted, how he was so weird and couldn't get along with other people. He was upset Marty couldn't get a job."

"You said Marty was so smart. How was he smart?" Beckett asked.

"Math, he was incredible with math. No one could understand what he talked about, but he was like a math genius. He was the real deal, we just needed to find someone who could make sense of everything Marty wrote down and said. My dad got him accepted into a graduate program at CUNY, but that only lasted about a year. It was when Marty got kicked out of school that Dad kicked him out for good. Said there was no way Marty could ever come live at home again."

"What happened to him after that?" Beckett asked.

"Well, I was just starting high school, and had a lot on my mind, so I just lost track of him, I guess. I hate to admit it, but I was relieved he wasn't around so he wouldn't embarrass me in front of my friends. You know how it is when you're in high school."

"So now that your Dad's dead, you and Marty got everything," Castle said. "And now that something happened to Marty, everything goes to you?"

"Well yeah, I guess, but hey wait - you don't think I killed him do you?" Marty protested. "I loved Marty, he's all the family I have left…. or had. Now I have no one," Jimmy frowned and hung his head for a moment before continuing. "I wanted to find him, to help him, to take him home. Marty just needed someone to be patient with him, to make sure he took his meds. He was a good guy, just different."

"What did you do to try and find him?" Castle asked.

"I Googled him, and found his name on some academic paper back from when he'd been a student at CUNY. The other name on the paper was Linderhoff, so I Googled him and found that he had been a professor at CUNY, but now he was a professor at Columbia, so I went to meet him and asked if he knew anything about where Marty was."

"And did he?" Kate asked.

"No, he barely remembered him."

"Then what did you do?" prompted Kate.

"Well, actually, not much. I didn't know what to do. I tried calling the police, but they didn't have anything either. I've been going around to all the shelters in the area, showing his picture, but nothing has come up. Nothing at all, until you guys called."

"So where were you last night?" Kate asked.

"I was working. I tend bar in Hoboken. I started at 5pm and was there until around 3am closing the place up, then I went home to bed. There's a ton of people who can vouch for me."

Beckett glanced at Castle and he shrugged in reply, not able to think of any more questions. They left Marty in the interview room and went to confer at Kate's desk. "What do you think?" she asked. "Do you believe him, that he really wanted to find his brother just to help him and give him half the money? He hasn't seen him in about 10 years, then suddenly he feels responsible for him after they inherit a bunch of money, money that all goes to him after his brother dies?"

"He certainly has motive," Castle answered, "but it sounds like he has a pretty good alibi too. I suppose he could have drugged Marty before going to work, but someone would have noticed Marty lying around the park during daylight. Marty would have had to been put there after dark for no one to notice him until morning."

"He could have had someone else do it," Kate suggested.

Castle thought about that for a moment. "I'll show his picture to Wanda, see if she recognizes him. And, I'll take the picture of Jimmy along with one of Marty over to the coffee shops at Colombia. Maybe someone saw them together over there."

"While you're there you should find this professor that Jimmy says he talked to and confirm that Jimmy really did meet him," Kate said.

Castle agreed, and then asked, "what do we do with Jimmy?"

"We hold him here until we check out his alibi. I'll call the police over in Hoboken and have them stop by the bar. You know, even if he was working last night, Marty's body was found at the George Washington Bridge and Hoboken is on the other side of that bridge. Depending on where the bar is, it might be a pretty quick trip to cross the bridge, dump the body, and then get back to work without anyone noticing he was gone. He could have done it while on break." Kate stood up and reached for her coat.

"And what are you going to do?" Castle asked, standing and grabbing his coat too.

"Head over to harass the tech guys about the GPS data on the cab. I figure if I show up personally, they'll jump my stuff to the head of the queue."

Castle saw Wanda first and showed her Jimmy's picture, but she did not recognize him. Next, he hit the coffee shops surrounding the Columbia University campus. After the fifth or sixth shop, he finally found someone who recognized Marty. A heavily pierced young girl with pale skin and jet black hair, working at one of the grungier shops, recognized him as a regular who spent almost every afternoon occupying one of the corner tables in the back of the shop, notebook spread out before him. Castle next showed her the picture of Jimmy Sawyer and she remembered him also. He'd been there with Marty a few days ago, she remembered clearly, because Marty had started yelling at Jimmy and making a scene and the staff had to toss both of them out of the shop.

So Jimmy had lied. After taking the girl's statement Castle called Beckett. "Yes, she's sure it was Jimmy Sawyer because they made a scene and had to be tossed from the place," he told Beckett excitedly.

"Well it seems the loving little brother isn't so altruistic after all," Kate replied. "We'll talk to him again and see how his story changes when confronted with this new information. You did good Castle. What are you going to do now?"

"'While I'm here, I'll track down that professor Jimmy said he spoke with to see whether he lied about that too. How about you, still hangin' with the techies?"

"Yes, but I convinced them to get my stuff done."

"Sounds like we're both making progress," Castle said. "I'll see you back at the station in about an hour."

Professor Morris Linderhoff's office was in the old math building on the Colombia campus. Castle found the office door open and the professor inside, seated behind a magnificent oak desk surrounded by shelves of textbooks and framed prints and degrees covering the walls. Two old leather stuffed chairs, looking more dignified than comfortable, were placed facing the desk. Professor Linderhoff himself looked the part of the distinguished professor - older, pasty white, mostly bald, with glasses, and wearing a grey, herringbone woolen suit with a silk maroon tie. The professor stood up when Castle knocked.

"Yes, what can I do for you?" the professor asked.

"Professor Linderhoff? I'm Richard Castle, I'm with the NYPD." Castle quickly flashed his plastic ID card that NYPD had given him as a special consultant. "I have a few questions if you have a moment."

"Oh, ok, yes, please have a seat" Linderhoff replied, gesturing to one of the chairs and re-seating himself behind the desk. He looked intently at Castle and frowned. "What are you here about, Mr. Castle?"

"It's about a former student of yours, Marty Sawyer, back when you taught at City University" Castle began, sitting down opposite the professor. "His brother claims he came to see you a few days ago."

"Hmm, let me think," said the professor, "ah yes, I recall now. A younger fellow." Castle took out the picture of Jimmy Sawyer and showed it to him. "Yes, yes, that's him. Said he was trying to find his brother. I'm afraid I wasn't able to help him though. I barely remember Marty Sawyer; it was so long ago."

"He was a graduate student of yours," Castle said, handing him the picture of Marty too. "He had some social problems though and only stayed year. But the two of you did publish one paper together."

The professor peered closely at Marty's picture. "Why is everyone looking for him?"

"He was murdered."

"Murdered, that's terrible! How?"

"He froze to death," said Castle. "His body was found at a park near the George Washington Bridge."

"Froze to death? But you said he was murdered."

"There's evidence he'd been drugged and left to die in the cold."

"Drugged? With what?" asked the professor.

"Ketamine, it's a tranquilizer. There was a needle mark in the back of his neck. It's pretty clear he was murdered."

"Do you have any suspects at this time?"

"We do, but I can't discuss any details," Castle replied. "You're sure you don't remember anything about Marty Sawyer?" Castle looked around the office as he spoke. It was neat and tidy except for a stack of old spiral-bound notebooks in one corner.

The professor turned to see what Castle was looking at and frowned, then turned back to face him. "Well, if we published a paper together I'll still have it. I keep copies of all my published work." The professor sat up in his chair and began nervously straightening the papers on his desk. "This is very disturbing, this talk of murder," the professor said, and, in fact, to Castle he did look suddenly upset. "Do you have any idea why he was killed? Was it a robbery gone bad?"

"No, nothing like that," replied Castle, watching the professor intently. "This was a premeditated murder. Someone wanted Marty dead for a reason." Castle and the professor locked eyes for a moment, and then the professor abruptly stood up.

"Mr. Castle, I think maybe I do remember something about Marty, something about him having trouble with drugs. But I'm afraid right now I must be off to teach a class. Why don't you walk with me and I can tell you everything I remember." The professor reached down and opened a desk drawer to retrieve something that he quickly put into his leather briefcase, then stood back up and moved toward the door.

Castle stood with the professor, "Sure Professor, that would be helpful," Castle said, giving the office one final glance as they headed out. They left the office together, Castle following the professor as they went down a hallway and then downstairs several flights, going down past street level. The professor noted Castle's confused look.

"We'll take the underground, to keep from going out in that horrible cold. Have you ever heard about the tunnels under Columbia?" the professor asked Castle.

"No, I haven't."

"Oh they're quite old. They date back to when some of these buildings were part of the old Bloomingdale's Insane Asylum."

"The Bloomingdale's Insane Asylum? I never heard about that."

"Oh yes, very interesting. It was founded by the faculty of Columbia in 1771, back when the school was called King's College. Much of the University is built on the grounds of the old Asylum. The tunnels are very old and quite extensive if you are the exploring sort. There's a maze of them underground, some mapped, some not so well known. But they do prove quite convenient for getting across campus on cold days like this and so the University maintains some of most used ones."

By now they had entered into the tunnels from the stairwell and were walking along a very old but well-lit tunnel. A few spider webs hung down here and there and the place had a very creepy feel to it. Castle couldn't imagine too many students using the tunnels, especially at night.

The professor cleared his throat and began talking again. "Now Mr. Castle, please tell me again, who are you and what connection do you have with the police? I can tell just by looking at you, your clothes, your watch, that you are not a police officer."

"I'm a special consultant."

"And what exactly is that? Do you have a badge, carry a gun?"

"No, nothing like that. I help conduct investigations."

"What led you to suspect this homeless person, Marty, had been murdered?" the professor asked.

Castle frowned at the question but kept walking. "He had a friend who believed Marty knew enough about living on the street to never freeze to death. She asked me to look in to it." Castle paused thoughtfully for a moment and then continued. "You know, Professor, I never did say that Marty was homeless," but the professor had stopped walking and Castle turned to see why. The professor stood there with a sad, tired expression, his briefcase in one hand and a gun in the other.

Beckett was back at the precinct and ready to talk again to Jimmy Sawyer. Castle hadn't returned from Colombia University yet so tried calling him but his phone went directly to voice mail. He was probably in the subway where there was no reception, heading over here. She decided to go ahead and interview Jimmy without Castle.

"Ok Jimmy, you lied to us," she began, studying his face for any reaction.

"About what?" he replied.

"We know you saw your brother a few days ago, before he died. We have a witness who put you with him at a coffee shop by Columbia University."

Jimmy swallowed nervously and ran his hand once through his hair. He leaned back in his chair and sighed, then began talking. "Ok, ok yes I was with him. We got in a big argument. I was afraid if I told you it would look bad."

"And lying to us doesn't look bad?"

"It's just he got so angry, he started shouting at me. We got kicked out of the shop."

"What was he so mad about?"

"That I wanted him to get back on his meds, to get him to a hospital and get taken care of. He screamed at me that they couldn't stop him, couldn't keep him from doing his work, that he had to do his work."

"His work? What was his work?" Kate asked.

"I don't know, some math stuff I guess. He had a big old notebook and it was filled with all these math formulas and stuff he'd written."

"What happened next?"

"He told me to go away, that I didn't believe in him, didn't understand him. I told him he could at least come home with me and we could live in our old house together, but he said no, his work was here, that he didn't mind living on the street, it was worth it. And then he left. And that was it, I swear, I never saw him again. Talk to the people I work with. I was at the bar all night, I never left. I swear…"

Kate studied Jimmy, trying to decide if he was telling the truth or not. He had motive for the murder, but if he was guilty, he was one of the best liars she had ever faced, and she had faced some of the best. No, she believed him, which made her think there was something more to this case than she had at first realized. She left Marty in the interview room and tried calling Castle again, but as before, his phone went directly to voicemail. He had to be on the subway. She decided to wait for him and they could think this case through together.

While she was waiting at her desk, one of the young guys from the tech department came over to he. "Detective Beckett" he called out, "I have that GPS data you've been waiting for." He handed her a piece of paper and waited expectantly for her approval.

"Derek, you didn't have to bring it up here, you could have emailed it," she said to him as she took the paper from him. She smiled, knowing full well he had made the trip just to see her. Kate was not above using her good looks to get her work expedited.

"No, no, that's ok" replied Derek. "After all, you came to see us, so I thought I'd return the favor. I like to get out of the computer lab every now and then." He looked around, taking in the scene of the nearly empty office. He had an awkward look about him that Kate thought was cute.

"Tell you what," she said, "why don't you help yourself to some coffee while I look this over. We have a great espresso machine in the break room."

Kate pointed the way and Derek smiled gratefully and headed over. She went to her whiteboard and put up the paper Derek had given her. It was a printout of the map of the GPS data showing the route of the murdered cabbie's last movements. She stared at it a moment and then felt a coldness wash over her. The map showed the last two stops the cabbie had made before being murdered. The first was outside Colombia University; the second, the park at George Washington Bridge. Whoever killed the cabbie had also killed Marty. She quickly pulled out her phone and called Castle again, willing him to answer, but instead hearing again only voicemail. She turned to the break room. "Derek" she shouted, "I need you to look something up for me."

He rushed over. "I need you look up the location of a cell phone for me," she told him. Derek sat down and began typing away. Quickly, he'd brought up the program the police used for tracking cell phones. Beckett gave him Castle's phone number and he typed it in. A map appeared on the screen with a flashing dot. "It doesn't have the current location, but it does have the last known location here," he said, pointing at the screen.

"Where is that?" Kate asked, pretty sure she already knew the answer.

"This building here at Colombia University. The math building."

Castle stared at the gun. It was a twenty-two. A dawning realization began to take shape in his mind. A dead homeless man, a dead cabbie…"You killed Marty," he said. "And that cab driver. But why?"

"I had no choice, it was time to put an end to the charade," the professor replied. His shoulders were slumped and he looked suddenly very tired and very old. "It's over now, and I must clean up after myself."

"What do you mean, 'clean up after yourself'" Castle asked warily, his eyes on the gun.

"First I had to get rid of Marty, then, I had to get rid of the cab driver who knew where I had taken Marty. I didn't think anyone would ever make the connection between the two. I'm sorry you did, so now, I'm going to have to get rid of you too." The professor sighed, but then a look of grim determination came over him. He waved the gun at Castle. "Now move, on down this tunnel and to the left."

Castle turned and started walking, his mind racing. What were his options here? Should he run? Turn and try to take the professor out? How good a shot could the old guy be? Could he be reasoned with? Castle decided on trying to reason with him, or at least keep him talking. "I don't understand why you had to kill Marty. What did he do?" he asked.

"It wasn't what he did, it was what I did," the professor replied. "I used him, built my career on him. All my work, everything I published, I stole from Marty. He was a genius, more brilliant than anyone I've ever met."

"Why didn't you just keep working with him?" Castle asked. "Why did you have to kill him? You could have built your career on interpreting his work. You knew he was mentally unstable, that he needed someone like you to present his work, make sense of it."

"Because they would have taken Marty away from me. I was just a lowly professor at CUNY, I never did anything until Marty came along. Once they saw that it was Marty who was the real genius, they would have taken him from me. He would be the one at Colombia, and I would be lucky to still have a job at CUNY."

"But why kill him now?" Castle asked, wanting to keep him talking.

"Because of his brother. Once his brother found him, what would I do? How would it look, that I allowed such a genius to live homeless in New York? And worse, once he started getting treatment, he'd see that I had taken credit for everything. I couldn't have that. I always feared he would find out." They had come to a side tunnel that turned off into darkness. "Now, turn here," the professor said, gesturing with the gun. "I will show you just how isolated some of these tunnels can be."

"What are you going to do with me?" Castle asked, turning and moving reluctantly down the dark tunnel.

"Oh, I have to kill you too I'm afraid" replied the professor. "I'm very sorry, but there is no other way."

"But you know you can't get away with it. The police know I'm here. You'll be found. Just give yourself up and we can work this all out." Thoughts of what to do were racing through Castle's mind. The professor seemed mentally unstable at this point and Castle doubted that he'd listen to reason. There was an edge to the professor's voice, a determination that hadn't been there before. The professor had crossed a line he couldn't return to.

"I know the police know where you are. But when do they start looking for you? I only need enough time to make my escape."

"Escape, where can you go?" Castle said. "They'll find you." They were headed deeper into the darkness and as Castle stepped forward he suddenly felt spider webs brushing against his face. Involuntarily, he jumped back, startling the professor. A shot rang out and Castle felt a searing pain suddenly at his side. He stumbled against the tunnel wall and clutched his side. Looking down, he saw a red stain slowly forming beneath his hand.

"I told you not to do anything," the professor hissed angrily. "Now look what you've made me do."

"You shot me," Castle said in disbelief. He stared at the professor and then back down to his side, where the dark stain was beginning to grow.

"Keep moving or I'll shoot you again," said the professor, waving the gun. "It doesn't much matter to me whether I kill you here or deeper in the tunnels."

Castle kept walking, but much slower now, leaning against the tunnel wall for support. Each step sent a stab of pain through him and he didn't know how much further he could go. Finally, the professor grew impatient with his slow pace and told him to stop, his voice shrill and panicked. "Ok, fine, that's enough, now sit down there, against the wall. Right there, and keep your hands where I can see them."

Castle did as he was told, gingerly lowering himself to the ground. He could feel the growing wetness of his blood at his side and tried not to think about it. Now what, he thought to himself. I'm pretty much out of options here. He looked over at the professor, who had sat down a few yards from him, the gun still pointed at Castle. The professor seemed unnerved at the site of Castle sitting there, bleeding. His other murders had been clean and quick; but this one, unplanned and accidental, was unsettling to him.

"I'm sorry I shot you Mr. Castle," he began hesitantly, "but it can't be helped. I need to clean things up, get rid all the evidence. No one must know that I have been living a lie all these years."

"But you know it's over now" Castle said, playing to the professor's uncertainty. "You can see that. It's finished. Don't make it any worse…." His side was killing him and his breathing was becoming fast and shallow from the worsening pain.

The professor suddenly sobbed inconsolably. "Any worse! How could it possibly be any worse! My life is ruined!" he wailed in despair. Castle thought now was a good time to make a move, to try to take out the old man, but when he started to get up, a wave of dizziness and nausea overcame him and he sat back, closing his eyes to ward off the sickening feeling in his stomach.

"All my life, I wanted to be somebody, be important," the professor began in a low voice. "I thought I was so smart. I got that first job at City and I was on my way. But I just wasn't smart enough. I didn't have it in me to do original work. And then along came Marty, crazy Marty." The professor chuckled silently to himself. "Marty was crazy, but he was brilliant, oh so brilliant and that's when I saw my chance. But then I realized if we kept publishing together, someone would figure out who the real genius was, that I was just a secretary. So I decided to use him, keep him to myself. I convinced him the drugs he took ruined his thinking, that he could reach much higher if he gave those up. And of course he believed me. It was almost too easy…."

The professor paused again, and again Castle tried to get up, but just sitting forward brought back the dizziness and Castle realized he wouldn't be going anywhere, that his life was now in the hands of this crazy, pathetic old professor.

"Do you know how hard it is to live a lie like that?" the professor suddenly asked, looking up at Castle. "Do you know what an agony every day is, every night when you lie in bed, knowing you're a fraud…knowing your colleagues would despise you and laugh at you if they knew the truth?" The professor sighed deeply. "Perhaps this is for the best, for all this to come to end. I'm so tired of it all…."

Suddenly Beckett's voice rang out, "Castle! Castle are you down here!"

"He's got a gun," Castle shouted out as loud as he could, but his voice was hoarse and he didn't know if Kate had heard him.

"Shut up!" the professor hissed, anger darkening his face. He stood quickly, his eyes darting around in panic. Finally, they settled on Castle, and he raised the gun and took aim. Castle cringed and turned his head away, helpless to do anything else.

A bright light suddenly filled the tunnel, blinding Castle. He heard Kate shout "Police, drop it!" and then immediately after, the thunder of Kate's gun. The professor's body was thrown backward on to the ground where he lay unmoving. Kate, her gun and flashlight held before her, cautiously stooped down to check on the lifeless body, and wrestled the twenty-two from the professor's fingers. Then she got up and rushed over to Castle, kneeling down in front of him. "Are you okay" she asked, shining the light over him. "Oh my god, you're shot," she said, then began shouting. "Derek, Derek, come here!"

"Who's Derek?" Castle asked, his voice barely a whisper now.

"He's a techie, out in the field for the first time," Kate replied, turning at the sound of Derek's hurried footsteps. "Derek, go back and bring help, now!" she barked. "Tell them we need an ambulance!"

Kate reached over and carefully moved Castle's hand aside to exam the wound. "You're bleeding pretty bad," she said, taking off her jacket and crunching it up in a wad to hold up against his side. He winced in pain but didn't complain.

"I'm sorry," he said, smiling weakly. He was so relieved to see her, he wanted to hug her but he couldn't move, and thought how he'd get blood on her clothes anyway so he just sat there gazing at her. She looked down at his side, her face full of concern. "It's just a flesh wound," he whispered, trying to sound brave, then closed his eyes and fainted.

It was a beautiful day in New York. After all that cold, the sun had finally come out and the sky was a crystal clear blue, like only a New York winter sky could be. The temperature was 38 degrees, balmy by recent standards, and only a slight wind. Castle stood with Beckett and took it all in, his arm around her, as much for support as for affection. They had kept him in the hospital for two days, and he'd spent another day at home in bed, but today he was outside, enjoying the view. Today they were setting Marty's ashes free.

They stood at the park where Marty had spent his last hours, at the foot of the George Washington Bridge next to the old Lighthouse. Castle, Beckett, and Jimmy Sawyer stood there, along with Wanda and her new friend, Todd. Todd had an odd way of blinking and didn't seem to notice you when he looked right at you, but he was Wanda's new alley companion. Wanda assured them that yes, Todd was quite crazy, but not to worry, he was harmless, unless you happened to look like Patrick Stewart, then watch out! Beckett had driven Wanda and Todd over here with them to let Wanda say goodbye to Marty also.

They were all standing at the edge of the park overlooking the Hudson River. Jimmy held up the simple jar holding the ashes of his brother and opened the lid. He turned the jar to the side and the ashes started falling out in a small grey cloud over the river. Jimmy shook the jar and held it upside down so that all the ashes escaped. Finally, he stood back and glanced over towards Beckett and Castle. "Well, there he goes" Jimmy said. He tried to smile but Castle could see he his eyes were tearing up.

Castle hugged Kate closer to him and she looked up. "Doing okay?" she asked quietly. He nodded yes, reassuring her he was fine. She had not wanted him to get out of bed yet, but he'd insisted. He was glad he came. He smiled at Wanda as she stood looking out at the river, hugging herself. She looked up and smiled back when they made eye contact. Todd stood alone, muttering to himself, pacing back and forth.

"What did Columbia say when you came to pick up Marty's notebooks?" Kate asked Jimmy.

"The head of the math department was there, trying to convince me that Colombia was really the best school for deciphering his notes, but I told them thanks but no thanks," Jimmy replied. He'd put the jar away and was standing there looking thoughtful.

"What are you going to do with the notebooks?" Castle asked.

"I haven't decided yet. Harvard, Yale, Berkeley, they've all asked about them," Jimmy smiled. "It's funny you know, Dad thought so little of him, and here now the top universities are fighting over his notes. They're calling him a genius. I always knew he was. Pity Dad never realized it." Jimmy turned to go. Castle and Kate followed, Castle leaning heavily on Kate for support. Wanda and Todd came along behind. After the shaking of hands and a few hugs, Jimmy got into his car and Kate, Castle, Wanda, and the muttering Todd got into hers and they departed the lonely park at the foot of the bridge.

When they returned to the apartment, Castle gratefully let Kate help him back to bed. The excursion had taken more out of him than he realized and his side was killing him. He reached for the bottle of painkillers at the bedside and popped one in his mouth. Kate pulled the blankets up over him and handed him a glass of water.

"How do you feel?" she asked. She'd been hovering over him the last few days and he was really quite enjoying it.

"I'm okay, just a little sore. Thanks for going with me. It gave some closure to it all, saying goodbye to Marty like that." Castle took a sip from the glass Kate had given him and set it on the table. He leaned back into the pillow and closed his eyes, trying to decide if he'd rather banter some more with Kate or just fall asleep.

She climbed on up onto the bed and sat down next to him. She wanted to spend the day here with him, make sure he was okay, but Gates had made it clear Kate had already had enough time off taking care of Castle. Gates wanted her top detective back at work today. "You going to be okay when I go in?" she asked. When he didn't answer she turned to see that he had already drifted off to sleep. She really didn't want to leave him alone like this, so she decided to hell with Gates, she'd stay here another day. They'd just closed two cases and surely that deserved some reward. She looked at him and brushed the hair off his forehead, gently kissing him, then quietly got up to phone Gates. She looked back, realizing he was the most important thing in her life, and vowing that she would never, ever let him solve his own case again. What would she do if she ever lost him?


End file.
